Naphthenic acid removal and conversion

ABSTRACT

Methods and apparatus relate to handling of organic contaminants in aqueous streams. The methods and apparatus enable removing the contaminants, such as naphthenic acids, from the aqueous streams and then converting the contaminants into hydrocarbons. The removing and converting of the organic contaminates results in treated discharge and generation of the hydrocarbons, which add to amount of hydrocarbon recovery.

CROSS-REFERENCE TO RELATED APPLICATIONS

None

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

None

FIELD OF THE INVENTION

Embodiments of the invention relate to methods and systems for treatmentand processing of fluid and naphthenic acid contaminants in the fluid.

BACKGROUND OF THE INVENTION

Water produced with oil from underground formations or generateddownstream in processes, such as desalting of the oil, forms waste waterstreams. The waste water streams can contain organics, such asnaphthenic acids, which are soluble enough in the waste water streams toprevent removal with oil-water separation. The naphthenic acidscontaminating the waste water streams present environmental concernswith respect to discharging of the waste water streams.

Factors influencing naphthenic acids removal include heighteningstringency of governmental regulations on ground discharge, increasingwater volume in the oil being produced, and rising levels of naphthenicacids in products as a result of more production from heavy oil. Thesefactors can prevent prior approaches for treatment of the waste waterstreams from being cost effective. Further, the prior approaches toremove the naphthenic acids from the waster water streams often produceadditional byproducts that still present problems for disposal.

Therefore, a need exists for improved methods and systems for handlingnaphthenic acid contaminants.

SUMMARY OF THE INVENTION

In one embodiment, a method includes filtering organic oxygen-containingmolecules from water by contacting the water with a sorbent for themolecules. The method further includes extracting the molecules from thesorbent by contacting the sorbent with a liquid hydrocarbon. Inaddition, converting of the molecules generates hydrocarbons.

According to one embodiment, a system includes both a naphthenic acidfiltering unit containing a sorbent for naphthenic acids and anaphthenic acid conversion unit coupled to receive effluent from thesorbent in fluid communication with a hydrocarbon supply. The filteringunit couples to a waste water supply containing the naphthenic acidsremovable by contact with the sorbent. The conversion unit contains acatalyst to convert the naphthenic acids in the effluent intohydrocarbons.

A method includes removing naphthenic acids from water by contacting thewater with a sorbent for the naphthenic acids thereby providing treatedwater and naphthenic acid loaded sorbent. The method also includesdrying the naphthenic acid loaded sorbent and extracting the naphthenicacids into diesel by contacting the diesel with the naphthenic acidloaded sorbent that is dried. Further, hydrotreating the dieselcontaining the naphthenic acids converts the naphthenic acids intohydrocarbons that add to constituents of the diesel.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with further advantages thereof, may best beunderstood by reference to the following description taken inconjunction with the accompanying drawings.

FIG. 1 is a schematic of a treatment and processing system for fluidswith naphthenic acid contaminants, according to one embodiment of theinvention.

FIG. 2 is a flow chart illustrating a method of removing from wastewater naphthenic acids made into additional fuel, according to oneembodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the invention relate to handling of organic contaminantsin aqueous streams. Systems and methods enable removing thecontaminants, such as naphthenic acids, from the aqueous streams andthen converting the contaminants into hydrocarbons. The removing andconverting of the organic contaminates results in treated discharge andgeneration of the hydrocarbons, which add to amount of hydrocarbonrecovery.

In some embodiments, produced water and/or process water resulting fromoil refining operations make up the aqueous streams. While describedherein with particular reference to the naphthenic acids, the organicconstituents may include the naphthenic acids, ethers, alcohols,aldehydes and/or ketones. The organic contaminants for some embodimentsthus include oxygen-containing molecules having a formula defined asC_(n)H_(2n−x)O_(y), with n selected from 6 to 46, x selected from −2 to12 and y selected from 1 and 2; or defined as C_(n)H_(2n−x)O₂, with nselected from 6 to 46 and x=0, 2, 4, 6, 8, 10 or 12.

FIG. 1 illustrates a treatment and processing system for fluids withnaphthenic acid contaminants. The system includes a filtering unit 100and a conversion unit 102. In operation, water containing naphthenicacids (H2O+NA) passes through the filtering unit 100 and exits astreated water (H2O), as indicated by solid lines. The water containingthe naphthenic acids contacts a sorbent for the naphthenic acids insidethe filtering unit 100. Exemplary sorbents include zeolites, carbon, andclays, such as kaolin and/or bentonite, and combinations thereof. Thenaphthenic acids adsorb onto the sorbent as the water containing thenaphthenic acids passes through the filtering unit 100 in which thesorbent is disposed. The treated water thereby contains less of thenaphthenic acids and has a lower naphthenic acid concentration than thewater containing the naphthenic acids that is input into the filteringunit 100. For some embodiments, the water containing the naphthenicacids contacts the sorbent at a temperature from about 1° C. to about80° C., from about 20° C. to about 40° C., or from about 23° C. to about28° C.

In some embodiments, the sorbent includes a zeolite with carbon presenton exterior surfaces and pore surfaces of the zeolite. The sorbentfanned of the zeolite may contain at least about 0.05% by weight carbon,at least about 0.07% by weight carbon, or at least about 0.10% by weightcarbon. The sorbent may define a surface area between about 40 and about400 square meters per gram (m²/g) or between about 150 and about 180m²/g. Further, the sorbent for some embodiments has a micropore volumebetween about 0.1 cubic centimeters per gram (cc/g) to about 0.5 cc/gand an average particle size between about 20 and about 120 microns. Aspent fluid catalytic cracking (FCC) catalyst (or spent FCC catalystfines) removed from a regenerator section of an FCC unit provides onesource for the sorbent formed of the zeolite with carbon. Contacting anFCC catalyst comprising the zeolite with a catalytically crackablehydrocarbon to form a catalytically cracked hydrocarbon product may thusalso result in preparation of the sorbent formed of the zeolite withcarbon.

Dashed lines indicate a subsequent flow path for achieving extractionand conversion of the naphthenic acids after stopping flow into thefiltering unit 100 of the water containing the naphthenic acids. Priorto initiating with operations utilizing the subsequent flow path, dryingthe sorbent removes remaining water on the sorbent. The sorbent oncedried then becomes immersed in a liquid hydrocarbon (HC) introduced intocontact with the sorbent to extract the naphthenic acids adsorbed on thesorbent. The drying and extraction may occur at or above thetemperatures for the contacting of the sorbent with the water containingthe naphthenic acids since increasing the temperature tends to speed upthe drying and extraction.

Desorption of the naphthenic acids from the sorbent regenerates thesorbent for reuse to continue removing the naphthenic acids from thewater containing the naphthenic acids. Agitation or mixing mayfacilitate transfer of the naphthenic acids from the sorbent into theliquid hydrocarbon. Amount of time in contact with the liquidhydrocarbon and contact conditions thereby influence level ofregeneration.

For some embodiments, the liquid hydrocarbon includes gasoline and/ordiesel even though other hydrocarbons can also be used to extract thenaphthenic acids based on tendency of the naphthenic acids to bedesorbed from the sorbent that is inorganic into the liquid hydrocarbonthat is organic like the naphthenic acids. The gasoline and/or dieselcontain molecules with from 4 to 21 carbon atoms so that the moleculesare small enough to facilitate flow and interaction with all surfaces ofthe sorbent for removal of the naphthenic acids. If the diesel is usedalone, the naphthenic acids removed may possess a molecular weightwithin a range of the diesel such that the naphthenic acids whenconverted form hydrocarbons that need not be removed from the diesel butrather are additive to the diesel.

The liquid hydrocarbon thereby passes in contact with the sorbent loadedwith the naphthenic acids and is removed from the sorbent as hydrocarboncontaining naphthenic acids (HC+NA). The hydrocarbon containingnaphthenic acids feed into the conversion unit 102. Exemplary conversionunits include deoxygenation based systems, such as hydrotreatingreactors or decarboxylating reactors with appropriate catalysts andconditions (e.g., above 200° C. and above 345 kilopascal (kPa)). In someembodiments, materials forming the catalysts include a noble metalcatalytic element, which may be in oxide form, dispersed on a support.Examples of the catalyst include cobalt/molybdenum, nickel,cobalt/nickel/molybdenum, or nickel/molybdenum dispersed on the support,such as alumina.

A hydrogen containing feed (H2) enters the conversion unit 102 forreaction with the naphthenic acids during the hydrotreating. Products ofthe hydrotreating include generated hydrocarbons and water mixed withthe liquid hydrocarbon input into the conversion unit 102 such that ahydrocarbon and water mixture (HC+H2O) defines an output from theconversion unit 102. For decarboxylation with the conversion unit 102,the products generated include carbon dioxide instead of water.

Separation of the hydrocarbon and water mixture divides the mixture intoa water phase and a hydrocarbon phase. In some embodiments, thehydrocarbon phase provides feed into a refinery for fractionating andfurther processing. The hydrocarbon phase for some embodiments mixeswith other refinery product streams or is used alone as a source offuel.

FIG. 2 shows a flow chart illustrating a method of removing from wastewater naphthenic acids made into additional fuel. In a water treatmentstep 200, the method includes filtering the naphthenic acids from wastewater utilizing a sorbent for the naphthenic acids. Drying of thesorbent occurs next in a water-to-hydrocarbon transition step 201.Extracting step 202 results in the naphthenic acids loaded onto thesorbent during the water treatment step 200 to be desorbed into a liquidhydrocarbon introduced into contact with the sorbent. After theextracting step 202, utilization of the sorbent switches back for reusein the water treatment step 200. In a reacting step 203, an effluent ofthe liquid hydrocarbon that is from the sorbent and contains thenaphthenic acids removed in the extracting step 202 enters a conversionunit having catalysts and conditions suitable to convert the naphthenicacids into generated hydrocarbons.

EXAMPLE

A laboratory experiment demonstrated an exemplary full cycle approachfor water treatment without byproduct waste. Test water contained 3.5grams naphthenic acid in 3.5 liters. The test water was passed through afiltration bed at ambient temperature and a flow rate of 14 cubiccentimeters per minute (cc/min). The filtration bed was charged with39.8 grams of FCC spent catalyst formed of a zeolite. The spent catalystwas determined to have retained 2.09 grams of the naphthenic acid.

The spent catalyst was next dried at ambient temperature. Once dried,300 grams of diesel was added to the spent catalyst and stirred for 5hours. A total acid number (TAN) of the diesel was then measured to be0.34 mg KOH/g.

The diesel containing the naphthenic acid was passed through ahydrotreating process using CoMo hydrotreating catalyst. Thehydrotreating was carried out at 4137 kPa, 340° C. and an hourly spacevelocity of 1.0 hr⁻¹. Respective flow rates for the diesel and ahydrogen feed for the hydrotreating were 20 cc/hr and 200 cc/min.Product from the hydrotreating was measured to have a TAN of 0.05 mgKOH/g, indicating the naphthenic acid had been converted intohydrocarbon.

The preferred embodiment of the present invention has been disclosed andillustrated. However, the invention is intended to be as broad asdefined in the claims below. Those skilled in the art may be able tostudy the preferred embodiments and identify other ways to practice theinvention that are not exactly as described herein. It is the intent ofthe inventors that variations and equivalents of the invention arewithin the scope of the claims below and the description, abstract anddrawings are not to be used to limit the scope of the invention.

1. A method comprising: filtering organic oxygen-containing moleculesfrom water by contacting the water with a sorbent for the molecules;extracting the molecules from the sorbent by contacting the sorbent witha liquid hydrocarbon; and converting the molecules into generatedhydrocarbons.
 2. The method system according to claim 1, wherein theorganic oxygen-containing molecules comprise naphthenic acid.
 3. Themethod system according to claim 1, wherein the organicoxygen-containing molecules include at least one of naphthenic acid,alcohol, ether, aldehyde and ketone.
 4. The method system according toclaim 1, wherein the liquid hydrocarbon comprises at least one of dieseland gasoline.
 5. The method according to claim 1, wherein converting themolecules into the generated hydrocarbons comprises hydrotreating theliquid hydrocarbon containing the molecules that are extracted from thesorbent.
 6. The method according to claim 1, wherein converting themolecules into the generated hydrocarbons comprises contacting theliquid hydrocarbon containing the molecules that are extracted from thesorbent with a hydrotreating catalyst containing cobalt and molybdenum.7. The method according to claim 1, wherein converting the moleculesinto the generated hydrocarbons comprises decarboxylating the moleculesthat are contained in the liquid hydrocarbon due to the extracting. 8.The method according to claim 1, wherein the sorbent comprises a zeolitewith carbon present on exterior surfaces and pore surfaces of thezeolite.
 9. The method system according to claim 1, further comprisingdrying the sorbent loaded with the molecules from the contacting withthe water.
 10. The method according to claim 1, wherein the organicoxygen-containing molecules have a formula defined asC_(n)H_(2n−x)O_(z); with n selected from 6 to 46, x selected from −2 to12 and z selected from 1 and
 2. 11. A system, comprising: a naphthenicacid filtering unit containing a sorbent for naphthenic acids, whereinthe filtering unit is coupled to a waste water supply containing thenaphthenic acids removable by contact with the sorbent; and a naphthenicacid conversion unit coupled to receive effluent from the sorbent influid communication with a hydrocarbon supply, wherein the conversionunit contains a catalyst to convert the naphthenic acids in the effluentinto hydrocarbons.
 12. The system according to claim 11, wherein theconversion unit is coupled to a hydrogen supply and the catalyst is ahydrotreating material.
 13. The system according to claim 11, whereinthe catalyst is a hydrotreating material containing cobalt andmolybdenum.
 14. The system according to claim 11, wherein the catalystis a material that facilitates decarboxylation of the naphthenic acidsin the effluent.
 15. The system according to claim 11, wherein thesorbent comprises a zeolite with carbon present on exterior surfaces andpore surfaces of the zeolite.
 16. The system according to claim 11,wherein the sorbent comprises a zeolite and the catalyst is ahydrotreating material.
 17. A method comprising: removing naphthenicacids from water by contacting the water with a sorbent for thenaphthenic acids thereby providing treated water and naphthenic acidloaded sorbent; drying the naphthenic acid loaded sorbent; extractingthe naphthenic acids into diesel by contacting the diesel with thenaphthenic acid loaded sorbent that is dried; and hydrotreating thediesel containing the naphthenic acids to convert the naphthenic acidsinto hydrocarbons that add to constituents of the diesel.
 18. The methodaccording to claim 17, wherein the sorbent comprises a zeolite withcarbon present on exterior surfaces and pore surfaces of the zeolite.19. The method according to claim 17, wherein the sorbent comprises azeolite with at least 0.05% by weight carbon present on exteriorsurfaces and pore surfaces of the zeolite.
 20. The method according toclaim 17, wherein the sorbent comprises a zeolite and the hydrotreatingincludes contacting the diesel containing the naphthenic acid with acatalyst comprising cobalt and molybdenum.